The soybean, Glycine max, is one of the major economic crops grown worldwide as a primary source of vegetable oil and protein. Growing demand for low cholesterol and high fiber diets has increased soybean's importance as a food. Over 10,000 soybean varieties have now been introduced into the United States, of which a limited number form the genetic base of lines developed from hybridization and selection programs. Johnson and Bernard, The Soybean, Norman Ed., Academic Press, N.Y., pp. 1-73, 1963.
Phytophthora is a highly destructive disease in soybean, and is only second to soybean cyst nematode in causing damage to soybean crops. This disease causes an annual yield loss of $300 million dollars (US) in North America (Wrather, J. A., and S. R. Koenning, (2006) Estimates of disease effects on soybean yields in the United States 2003 to 2005. J Nematol 38: 173-180), and occurs in most of the soybean-growing areas in many different countries. Phytophthora sojae, is a soilborne, oomycete pathogen and can cause Phytophthora root and stem rot (PRR), pre- and post-emergence of damping-off, yellowing and wilting of lower leaves, and death of soybean plants. More than fifty-five races of P. sojae have been identified (Slaminko et al., (2010) Multi-year evaluation of commercial soybean lines for resistance to Phytophthora sojae. Plant Disease 94). Developing soybean line resistance is one of the primary methods to control this disease. The Rps1-c (50%), Rps1-k (40%), and Rps1-a (10%) traits are the most commonly used genes that are introgressed into germplasm to provide protection to P. sojae (Slaminko et al., 2010).
Markers that are linked to the phytophthora resistance trait, Rps1-k, include RFLPs, SSRs and SNPs. The markers identified in this disclosure can be used for phytophthora resistance genotyping to support a breeding program. Using the presently disclosed markers to perform phytophthora resistance genotyping in support of a breeding program provides: cost and time savings; early selection of desired progeny; and more accurate and rapid commercialization of phytophthora resistant soybean varieties.